This article is from the Organ Transplant FAQ, by firstname.lastname@example.org (Michael Holloway) with numerous contributions by others.
Candidates and donors are matched by data, not rank. The only thing
you could be "ranked" by, in theory, is your waiting time. You could
be #1 on your local list by waiting time, having waited longer than
everyone else. However, if you're blood type B and a type A organ
comes along, you'd automatically be excluded. The same is true for
organ size, tissue match, etc. Given that all donors and all
candidates differ in some respects, you could be 20th on the list for
one offer, 3rd for the next, then 57th, then 1st.
Even if you're at the "top of the list," you may not get the organ.
Perhaps you have a complication that would preclude getting a
transplant for a few days or weeks. Maybe in reviewing the lab work
or donor history the transplant team has cause to defer the offer.
Perhaps, if you're highly sensitized, the initial crossmatch is OK but
the final crossmatch comes back bad. There are lots of scenarios.
Any refusals and the explanations would be submitted to UNOS.
Organs other than kidneys are most often transplanted into one of the
first 10 candidates identified on the match run. For kidneys that
rate is much lower, particularly because of highly sensitized patients
with adverse crossmatches.
With specific, written permission from the patient and from the
listing center, UNOS can provide the basic information on patient
listing (date of entry, current medical status, etc.). But I'd *beg*
you to call the center first on this if you have any questions! And
again, for all the reasons above, this would be meaningless as an
expression of your "rank" for a transplant.
For more detail: